The invention relates to a power miter saw for use in making controlled angular cuts in a work piece. More particularly, the invention relates to a detent mechanism for quickly and accurately setting the saw to any one of a plurality of indexed angles and for overriding the detent mechanism in order to allow for micro-adjustment of the indexed angle.
Miter saws have been used in carpentry, cabinet-making, and other crafts to create angular cuts in a work piece. Typically, the miter saw has a rotatable turntable on which the saw is mounted. The turntable is rotated to place the saw at a desired angular setting relative to the work piece. A detent mechanism comprising an indexing detent and a series of detent receiving recesses, is provided which operates to lock the rotatable turntable at frequently used angles which will be termed preset angles. Detent recesses are provided at these preset angles which typically are at 15, 30, 45, 60, 75, and 90 degrees. The detent is constantly biased, via some biasing means, so that it will be urged into the detent recess with which it is aligned. The biasing means provides enough force to automatically center and then hold the turntable at the precise preset angle.
While providing an indexing detent is generally desirable, the tendency of the detent to seat in the predetermined indexing detent recess can pose problems. For example, very often the angle required to fit a perfect joint for a chair rail in the corner of a room is not exactly 45 degrees. It may be 441/2 degrees or 451/2 degrees. An attempt to make a 1/2 degree adjustment away from a preset angle on a miter saw having a conventional indexing detent mechanism is difficult. During such an attempt, the operator would typically rotate the turntable slightly and force the detent from a fully seated position in the detent receiving recess. However, the detent would not be completely out of the recess because only a small adjustment is being made. In this situation, the spring biased action of the mechanism will tend to force the turntable back from its micro-adjust position to the preset angle position thereby allowing the detent to once again, seat solidly in the detent recess provided for that preset angle.
Thus, it is desirable to provide an override mechanism which can override the indexing detent to allow for micro-adjustment relative to the preselected detent angles, and provide a means for locking the turntable in the micro-adjust position.
U.S. Pat. No. 5,042,348, issued to Brundage et al., illustrates a compound miter saw having a rotatable saw unit mounted on a turntable and including an index spring in frictional contact with the supporting frame and turntable. While the index spring provides some frictional resistance against rotational motion of the turntable relative to the supporting frame, there is no detent mechanism or detent override mechanism.
U.S. Pat. No. 4,559,857, issued to Grossmann et al., illustrates a chop saw having a turntable detent mechanism which includes an elongated push rod for selectively releasing the detent mechanism. That chop saw does not include a detent mechanism override nor a means for locking the turntable in a micro-adjust position while the indexing detent is disengaged.
U.S Pat. No. 4,011,782, issued to Clark et al., show a power miter saw having a detent and locking means for securing the turntable in a selected position. However, that miter saw does not include a detent override nor a locking means that may be disabled to free the turntable for micro-adjustment away from a preset angle.
U.S. Pat. No. 3,821,918, issued to Niehaus, illustrates a spring biased ball detent mounted in a blind bore to automatically locate the saw at a preset angle. That the detent mechanism is not selectively engageable nor permanently locked out of position for micro adjustment.